ATAATAPI

ATA/ATAPI refers to the family of computer bus standards used to attach storage and related devices to a motherboard. The term covers the original AT Attachment (ATA) interface, commonly known as IDE, and the AT Attachment Packet Interface (ATAPI), which enables non-disk devices to communicate over the same bus. The standards are part of the wider IDE/ATA lineage developed by industry groups including INCITS.

ATA defines the parallel bus that carries data, address, and control signals between a host controller and a device such as a hard disk. A typical PATA interface uses a 40-pin ribbon cable and supports two devices per channel: master and slave. Early transfer modes included programmed I/O (PIO) and DMA, with later revisions delivering higher speeds under Ultra DMA (UDMA), up to ATA-133 (about 133 MB/s).

ATAPI extends ATA by carrying command packets rather than raw ATA commands, allowing devices such as CD, DVD, and magneto-optical drives to share the same bus. The host issues a PACKET command that contains a SCSI-like command set, and the device responds accordingly. ATAPI shares the same electrical interface as ATA devices; the main difference is the command protocol and the type of device.

Today, Parallel ATA has largely been superseded by Serial ATA (SATA) and other interfaces, though ATAPI remains widely used on optical drives and other accessory devices, and the term IDE remains common in consumer parlance for ATA-based storage.